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noz
Before anyone says it I know I'm being lazy but in my defence it's brass monkey weather out there tonight.

My heater isn't exactly broken. It's just that hot air comes out of the dash vents but not from the windscreen vents or the footwell vents. Only cold air comes out of those even at the same time as hot air out the others.

Has anyone come across this particular permutation before? If so, what was the fault? If I can at least narrow down the likely candidates I may be able to fix it before my fingers drop off with the cold.

Cheers

noz sad.gif
Big-Green Balls xm
Hello Noz

Have you had a look at the servo that controls the heater flaps ???

Heres a link that might help you if you get stuck
http://www.citroen-ds-id.com/ under tecnical !!! biggrin.gif

Tells you how to look at the flap servo in better detail than me just trying to wright it down ( or to lazy lol) rolleyes.gif

Hope you don`t freeze them green things off biggrin.gif

It sounds like it will be down the the servo has usual rubbish made plastic gears or bad conection worth a look Itsss gettinnnng collllllllder ohmy.gif

uligrafenstein
Hi Noz,

I have exactly the same symptomes in my Y3 v6/24v. I did check the 3 Flapservos, one was stuck (the one controlling the air flow direction). Now I do have air coming where I want, but still it comes cold from the windscreen vents or the footwell vents. If you already could identify the fault, please dend me a mail. I will do the same, if I should be faster.
As far as I learnd in another forum (www.andre-citroen-club.de) it could be a faulty cooling liquid sensor (one of the three mounted on a V6, don't know for other engines, which is used in combination with indoor and exterior temperature to control the air temp. However, I don't believe that this would explain the temperature contrast between windscreen/footwells and the other vents. So I suspect either a problem in the heater unit (would like to see one without extracting mine) or incorrectly connected air conducts.

Would be great if we could solve the coldfinger/cloudy windscreen problem before winter really strikes hard.

cheers

Uli
noz
Thanks guys,

However, the car with the heater problem is now off the road pending a head gasket replacement plus whatever I find when the head comes off. The heater problem will have to wait until I've fixed the head problem.

The other 2.5 is now on the road after a long absence. It's going fine.

I work away from home a lot so weekends is all I have to work on the car so it might be a while.

Cheers

noz cool.gif
uligrafenstein
Hi again, Noz,

I did trace down the cold air problem on my 24V. Electronic and sensors worked all fine, flap servos, too, although one of the three had to be repared. Reading out the A/C ECU did not give an error (but at least I have now a nice liltle box with LED and switch to read out the other ECUs in case of problems). I checked all the air conducts (fine). So I thought that the fault must be in the air mixing box, which seems to be one the first to be fitted into the car. To check the cold/warm air internal flaps, the heater matrix has to come out. All looked fine, inside the box, too, but when trying to wash out the heater matrix, I realized that only the uppermost U-shaped internal tube (one out of eight) was active. This perfectly explains the symptomes you and I have: the middle dash board vents receive air from the upper part of the space downstreams (after) the matrix, whereas both windsreen and footwell air comes from the lower part. In order to check, heat up tthe car and just switch the air direction from middle/down to middle only, and check by hand the air temperature come out of the middle vents. If you realize a significant cooling for the middle only position, I am sure that your heater matrix is blocked to at least half.

I tried to clean the heater matrix using all kinds of weak acids, and got about 50% of the matrix back to life. However, I decided that a new matrix and O-rings should be the best.

I only hope for you that your XM is left hand driven, because it is much less work to exchange the matrix than in a right hand driven.

Uli
Peter.N.
The most effective way I have found of clearing blocked matrixes? is with compressed air. Disconnect the hoses the engine end, flush the matrix through with the hose pipe, in both directions and then apply the air line to each end alternately until the water come out clear, filling the matrix from the hose between each blast. I have never burst a matrix during this process but I suppose its always possible.

Peter.N.
noz
Scrapping the 2.0CT gave me a great excuse to strip things to bits that I would have otherwise shyed away from on my daily runabout. I successfully removed the matrix without destroyoing it. I had to hacksaw the top right corner off the plastic header tank just above the top hose connection. After that it was easy. I saw that the three plastic spring clips were damaging the fins so I deliberately broke them off. The matrix is held in place by a fixing screw in any case.

I washed the matrix out in the kithen sink. I flushed it for a while in both directions until the brown colour disappeared and I could feel the hot water at each of the tube end returns on the opposite end from the plastic tank.

I'll replace the matrix in the '96 Blue 2.5 with the spare cleaned matrix when I finally get around to taking the head off.

The blocked matrix theory seems the best yet. There's only one electrically controlled flap on the heater itself so there's not much to go wrong. The other 2 directional flaps are controlled by a cable from the knob on the dash. The only other flap is also controlled by a cable. It's the fresh/recirc air selector slider at the bottom of the heater controls. The single flap either allows air to be drawn from the cab into the intake of the fan or from the outside via the space below the scuttle panel.

Cheers

noz cool.gif
uligrafenstein
Hi Noz,

After one day of detarting and washing with a domestic cleaning product, I got out quite a lot brown-red stuff. It still is not finished but I'm now quite confident that I can reuse the old matrix, too.

What did you do to replace the foam around the three slim sides of the matrix? I thought to use '3M'-like foam tape (the kind of tape you can buy for bad old windows).

Don't forget to find the replacement for the sealing O-rings.

Uli

noz
Uli,

I've just got the matrix out of the scrap car. I haven't fitted it yet to the other car. The foam tape you mention is probably what I'd use.

Cheers

noz cool.gif
Peter.N.
Funny thing, but I have just noticed the the air from the footwell vent on mine is not as warm as that from the dash, wouldn't have thought anything of it until you lot started. Thanks!

Peter.N.
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